The Newsletter of Crawford Broadcasting Company Corporate Engineering OCTOBER 2020 • VOLUME 30 • ISSUE 10 • W.C. ALEXANDER, CPBE, AMD, DRB EDITOR Microwave Links serviceable antennas that would work, so we About a year ago, in an effort to deal with a scheduled the work for mid-September. Our shortest batch of orphaned Part 101 microwave links in path, KLZ, would be first. Should be easy, right? several markets, we purchased new Cambium Existing paths, existing antenna mounts and all that... equipment. The big question Amanda will tell was whether we could use you more about this project our existing antennas with in her column, but… the Cambium radios. The Keith was in the answer was anything but middle of a move, and clear. Amanda has yet to acquire We were able to the ability to be in two obtain adaptors that places at once, so it fell to converted both Andrew and me to work the studio end Radio Waves antennas for while Amanda would go the Cambiums. We believed with the other crew out to that our Trango-branded 3- KLZ. But before starting, I and 4-foot antennas were wanted to see the radios on either Andrew or Andrew the backs of the antennas so knockoffs. At one point in I could be certain that the the late summer of 2019, I Yes, the “new” antenna for the KLZ 11 GHz link adaptors would work with checked and found that the says “Eventide” on it. No, it’s not an Eventide the used antennas. And it’s a adaptor would indeed fit the antenna, but Amanda had some cool Eventide good thing I did, because antennas we had on the roof stickers that came with the new delay units, so while the Commscope at our Denver facility. rather than leaving the radome bare… antenna worked fine on the Several months Andrew dish, we did not later, when we had the radios on hand, we sent Derek have the proper adaptor for the Radio Waves dish. Jackson up with Amanda to do the installation. The Back to the drawing board. adaptor fit just fine… but the waveguide from the The 3dB folks sourced the proper adaptor feedhorn would not fit the Cambium radios. And for the RW dish and got two of them overnighted to unfortunately, the feedhorn in the Trango-branded us – two because we would also need one for the dish antennas were integral and could not be swapped KLTT link the following week, assuming the KLZ out. So… we would have to get new antennas, ones link work went okay. that fit. What a pain! The next morning, we met on the loading And then along came COVID-19. dock at our studio building, and the adaptors arrived Everything was put on hold. It was only in July that before 8:00 AM. We put it on the 4-foot RW dish, we again started looking at this. Our friends at 3dB and the radio fit perfectly. So off Amanda went with Networks came out and did a site survey at the studio one crew and up I went to the roof with the other and the three transmitter sites where the older Trango crew. radios were in use. 3dB had some used but 1 The Local Oscillator October 2020 tower. My working theory is that there is a current detector in that power supply/injector, and the RF was fooling the comparator into “thinking” the radio was drawing too much current, causing the supply to crowbar. Derek observed the power supply coming on and producing full voltage, then shutting down, then powering up, then shutting down, ad nauseam. The crowbar would clear when the voltage went to zero and the supply would come back on… until it crowbarred again. As soon as we would switch to the ND mode on the other tower, the power supply would stay on and the radio would reboot. So… we pulled out the Cambium supply/PoE injector and Derek hauled up an Omrin DIN-rail 48-volt supply and installed that, powering the radio directly. That worked. With RF on the tower, we had good throughput with no further issues. In the process of installing the KLZ and KLTT Cambium equipment, we had a couple of occasions when parts were needed at the top of a tower and it would be a long climb down and back up. It occurred to me that we might be able to deliver the needed parts with our drone, so I rigged a 12-foot piece of nylon strap and up it went. At KLZ, I rigged a slip-knot through a Ziplock bag with the parts One of the new Cambium PTP820S 11 GHz radios inside. That worked great. installed on the back of a pre-owned antenna on the KLZ west tower. It was a very, very long day, but by twilight that evening, we had the antennas changed out, the new radios in and radiating, and the path aligned. The link was passing data at the rate we expected, so we were about to call it a success. And then, as soon as the climber was off the west tower at KLZ, we switched back to the DA mode, and as soon as we did, the link died. As in dead. As in can’t even ping the radio on the tower. And no signal received at the other end. It didn’t take long to figure out that the 2 kW of 560 kHz RF in that west tower was somehow killing the radio. The question was, what could we do about it. We scheduled our friend and engineer- The tower worker reaches out and takes hold of climber Derek Jackson to go up the tower to look the cable clamp that Jordon flew up to him with things over. our drone. I was thinking that the 56-volt MOVs in the At KLTT, at the suggestion of my son-in- Ethernet surge suppressor installed in line with the law Jordon, who is a professional drone pilot, I network cable up on the tower were firing as a result rigged the strap with a couple of medium binder of the RF riding on top of the 48-volt DC PoE. That clips, attaching one to the drone’s landing gear and seemed like as good a guess as any, but Derek the other to the part that was needed up on the tower. quickly figured out that the issue was the Cambium Since he was standing there, I asked Jordon to fly the power supply/PoE injector. It was shutting down part up the tower, and he did. It was windier than it when we would put any amount of AM RF on that had been when I flew the parts up the KLZ tower, but 2 The Local Oscillator October 2020 he got it done, putting them right into the climber’s the end of the line? In both the KLZ and KLTT cases, hands. we simply had the climber go up a short distance to We’re going to have to do some the top of the tower to retrieve the items, but what experimenting to see what kind of payload weight would we do if the work were farther down a tower? our drone will safely carry. We also need to see how All questions to be answered through close we can get to the tower structure – can we get experimentation. close enough for the climber to reach out and grab The New York Minutes By Brian Cunningham, CBRE Chief Engineer, CBC – Western New York Hello to all from Western New York! I truly felt sorry for Stan, and his former The Oxford English Dictionary defines employer, for I know what he accomplished over the passion as a strong and barely controllable emotion, years could not be replicated by anyone else. His enthusiasm or fondness former employer is still towards someone or searching for a suitable something that provides you replacement in a dwindling great joy or anger. pool of reliable and Through the years, competent applicants. I have met perhaps hundreds Even after 50 years of broadcast engineers and since I first started in the made friends with many of broadcast business, I still them, conversing either look forward to coming to through social media or work and solving problems, telephone from time to time. figuring out better ways of I recently reached out to one doing things, and learning such individual whom I had new techniques and met some 30 or so years ago technology changes. I am so at a Kentucky Broadcasters thankful that I have the Association award banquet in Louisville, Ky. opportunity to do daily what brings me joy and Stan and I hit it off instantly, and remained challenges, and I pray that I never lose that passion in contact at least monthly, until the pandemic hit in that has driven me for most of my life. mid-March. I called Stan recently to see how things Each year, the week after Labor Day, Nora were going for him and to catch up with how things and I pack up and head to Eastern Pennsylvania for a were going in his world. I was truly surprised to hear week of relaxation in Gettysburg. This year is the that he had quit broadcast engineering and was first time in 28 years that we have not made the trek working as a marketing consultant for a major to our favorite destination, largely due to the COVID- Fortune 500 company.